diff --git a/src/llmtuner/chat/stream_chat.py b/src/llmtuner/chat/stream_chat.py
index 07fc7bf0..73c8f332 100644
--- a/src/llmtuner/chat/stream_chat.py
+++ b/src/llmtuner/chat/stream_chat.py
@@ -23,7 +23,7 @@ class ChatModel:
         self.generating_args = generating_args
 
     def process_args(
-        self, query: str, history: List[Tuple[str, str]], prefix: Optional[str] = None, **input_kwargs
+        self, query: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = None, **input_kwargs
     ) -> Tuple[Dict[str, Any], int]:
         prefix = prefix if prefix else self.source_prefix
 
@@ -59,7 +59,7 @@ class ChatModel:
         return gen_kwargs, prompt_length
 
     def chat(
-        self, query: str, history: List[Tuple[str, str]], prefix: Optional[str] = None, **input_kwargs
+        self, query: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = None, **input_kwargs
     ) -> Tuple[str, Tuple[int, int]]:
         gen_kwargs, prompt_length = self.process_args(query, history, prefix, **input_kwargs)
         generation_output = self.model.generate(**gen_kwargs)
@@ -69,7 +69,7 @@ class ChatModel:
         return response, (prompt_length, response_length)
 
     def stream_chat(
-        self, query: str, history: List[Tuple[str, str]], prefix: Optional[str] = None, **input_kwargs
+        self, query: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = None, **input_kwargs
     ) -> Generator[str, None, None]:
         gen_kwargs, _ = self.process_args(query, history, prefix, **input_kwargs)
         streamer = TextIteratorStreamer(self.tokenizer, timeout=60.0, skip_prompt=True, skip_special_tokens=True)
diff --git a/src/llmtuner/extras/template.py b/src/llmtuner/extras/template.py
index 67c82c7a..88469d5c 100644
--- a/src/llmtuner/extras/template.py
+++ b/src/llmtuner/extras/template.py
@@ -1,4 +1,4 @@
-from typing import List, Optional
+from typing import List, Optional, Tuple
 from dataclasses import dataclass
 
 
@@ -139,25 +139,33 @@ class Template:
         else:
             raise ValueError("Template {} does not exist.".format(self.name))
 
-    def get_prompt(self, query: str, history: Optional[list] = None, prefix: Optional[str] = "") -> str:
+    def get_prompt(
+        self, query: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = ""
+    ) -> str:
         r"""
         Returns a string containing prompt without response.
         """
         return "".join(self._format_example(query, history, prefix))
 
-    def get_dialog(self, query: str, resp: str, history: Optional[list] = None, prefix: Optional[str] = "") -> List[str]:
+    def get_dialog(
+        self, query: str, resp: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = ""
+    ) -> List[str]:
         r"""
         Returns a list containing 2 * n elements where the 2k-th is a query and the (2k+1)-th is a response.
         """
         return self._format_example(query, history, prefix) + [resp]
 
-    def _register_template(self, prefix: str, prompt: str, sep: str, use_history: Optional[bool] = True) -> None:
+    def _register_template(
+        self, prefix: str, prompt: str, sep: str, use_history: Optional[bool] = True
+    ) -> None:
         self.prefix = prefix
         self.prompt = prompt
         self.sep = sep
         self.use_history = use_history
 
-    def _format_example(self, query: str, history: Optional[list] = None, prefix: Optional[str] = "") -> List[str]:
+    def _format_example(
+        self, query: str, history: Optional[List[Tuple[str, str]]] = None, prefix: Optional[str] = ""
+    ) -> List[str]:
         prefix = prefix if prefix else self.prefix # use prefix if provided
         prefix = prefix + self.sep if prefix else "" # add separator for non-empty prefix
         history = history if (history and self.use_history) else []